1. Field of the Invention
The present invention relates to a crawler system and a crawler link structure.
2. Description of the Background Art
As shown in FIG. 9, a track-laying wording vehicle such as a hydraulic shovel comprises a lower traveling body 51, an upper swirling body 52 and a working machine 53 connected to the upper swirling body 52. The lower traveling body 51 comprises a crawler system 54 as a running gear. The crawler system 54 comprises a crawler 55 in which pairs of opposed right and left links are connected endlessly in general (refer to patent document 1: Japanese unexamined Patent Publication No. 2001-347972 (pages 4 to 9, FIGS. 12 and 17)). The crawler 55 is wound around, an idler 56 and a crawler sprocket 57.
According to a crawler disclosed in the patent document 1 and the like, as shown in FIG. 10, ends 61 and 62 of adjacent links 60 in the longitudinal direction overlap with each other and the overlapping ends 61 and 62 of the opposed right and left links 60 are connected, through connecting members 63. In this case, the link 60 comprises a central thick part 64, one end 61 positioned inside and the other end 62 positioned outside. Through holes 65 and 66 are provided in the ends 61 and 62. In addition, through holes 67 are provided in the central thick part 64. A through hole 69 is communicated with a through, hole opening on the side on which a shoe plate 68 is mounted.
In this case, the connecting member 63 comprises a connection pin 70 and a bush fit around the connection pin 70. The links 60 are endlessly connected by inserting the connection pin 70 between the opposed links 60 through the bush 71 in a state in which the ends 61 and 62 of the links 60 overlap with each other on the right and left sides. At this time, both ends of the connection pin 70 are pressed to the through holes 66 of the ends 62 arranged outside of the links 60, and both ends of the bush 71 are pressed to the thorough holes 65 of the ends 61 arranged, inside of the links 60. In addition, the shoe plate 68 is made to overlap with a mounting face of the link 60 and a bolt member 72 is inserted to the through hole provided in the shoe plate 68 and the through hole 69 of the thick part 64 of the link 60, so that the bolt member 72 engages with a nut member 73 provided at the through hole 67 of the thick part 64. Thus, the shoe plate 68 can be mounted on the links 60 connected endlessly. In addition, reference numeral 74 denotes a sealing member in FIG. 10.
Thus, according to the conventional crawler system, the number of parts is large and its assembling workability is low. In addition, since the number of parts is large, its cost is increased and its inventory control of the parts is complicated. In addition, as shown in FIG. 11, since the connecting member 63 engages with a concave tooth 77 of concavo-convex teeth 76 of the crawler sprocket 57, the connecting member 63 receives sprocket loads, so that it is necessary to enhance hardness of the connecting member 63. Furthermore, the center of link motion corresponds to a shaft center of the connecting member 63 at the time of engagement of the crawler sprocket 57. Therefore, the bush 71 of the connecting member 63 rubs against the concavo-convex teeth 76 of the crawler sprocket 57, causing the bush 71 to be damaged. Consequently, its durability is low.